Create CONTRIBUTING.md
Mention [ci valgrind].
Include Jen's reminder about creating PR's
Make Marker into ModelComponent that derives from Station and modify tools accordingly.
Main changes in Marker:
1. Marker implementing ModelComponent interface.
2. bodyName property changed into Connector to a RigidFrame (in OpenSim::Station)
3. fixed flag has been removed (assumed false, tools now work but will be updated accordingly)

To support Marker functionality, RigidFrame has been amended with method getBody() to return ref. to the Body that the RigidFrame is attached to.
Replace unnecessary const_cast with dynamic_cast (since SafeDowncast doesn't handle const pointers)
Couple more comments.
Merge branch 'matt_ayman_frames' of https://github.com/opensim-org/opensim-core into matt_ayman_frames
Merge .travis.yml from master so that wrapping is not built on gcc.
Up XMLDocument::LatestVersion to account for change in deserializationof Marker, also remove unused method from Marker.
Expose Station to SWIG wrapping so that subclass Marker behaves properly.
Expose Station class in SWIG to fix python test cases
Remove debugging lines and fix authorship in cpp files
Merge branch 'matt_ayman_frames' of https://github.com/opensim-org/opensim-core into matt_ayman_frames

Conflicts:
	OpenSim/Wrapping/Java/swig/javaWrapOpenSim.i
Merge pull request #183 from opensim-org/jimmydDoxygenExperiment

Doxygen layout and format changes. Moved doxygen related files to opensim/doc
[readme] Update travis build status image.

...to reference master branch instead of latest build.
Remove GUI license. Rename API license.

Also updated the year in the copyright.
[license] Moving author list to CONTRIBUTING.md.
[contrib] Add contributors list.
[contrib] Clean up contributors list.
Formatting, doxygen changes, and one code typo.